Defibrillator pad assembly and method for using same

ABSTRACT

The defibrillator pad of the present invention comprises a lower layer of electrically conductive tacky polymer and an upper layer of filamentous carbon fabric containing carbon fibers coated with an electrically conductive polymer. The pad is placed on the patient&#39;s chest with the polymer layer facing downwardly in contact with the patient&#39;s chest and with the carbon layer facing upwardly for engagement with the electrodes of the defibrillator paddles.

BACKGROUND OF THE INVENTION

This is a continuation-in-part of copending application Ser. No.456,497, filed Dec. 26, 1989, now U.S. Pat. No. 4,998,536.

This invention relates to a defibrillator pad assembly and a method forusing same.

Defibrillation is a process used for patients encountering fibrillationof the heart. The defibrillation process involves placing two electrodepaddles on the patient's chest and applying a high density, electricalcurrent to the patient so as to stimulate the heart and correct thefibrillation of the heart.

Dry skin on a patient causes the interface between the metaldefibrillator paddles and the skin to have a high impedance. This cancause severe skin burns and may cause a significant reduction in thecurrent delivered to the heart so as to prevent successfuldefibrillation.

Present methods for applying the defibrillator paddles to the skininvolve the use of electrically conductive gels which are applied to thepatient's skin and which are also applied to the defibrillator paddles.Often the gel is incompletely applied leaving bare spots between thepaddle and the patient's. These bare spots may result in burning of thepatient's skin during discharge. Also, it is necessary for the user ofthe paddles to continue to apply pressure between the paddle and thepatient's skin in order to insure a positive electrical contacttherebetween.

Another disadvantage of presently used gels is that they are messy.Also, the gel often gets on the user's hands and arms, making itdifficult for the user to perform other functions such ascardiopulmonary resuscitation.

Another presently used method for defibrillating involves the use ofmoisturized polymer pads which are enclosed within an airtight envelope.The pads are removed from the envelope and placed on the patient's chestimmediately prior to use. Then the defibrillator paddles are placed overthe pads in preparation for their use. The disadvantage of thesemoisturized pads is that they tend to harden and become brittle afterprolonged exposure to the atmosphere. Furthermore, they do not provide astrong adhesive bond between the pad and the patient's chest, andtherefore, they sometimes slip or move after use.

Another method for defibrillating involves the use of a pad such asdisclosed in U.S. Pat. No. 4,779,630. The method disclosed in thispatent shows a polymer pad which is tacky and adhesive in itscharacteristics. It is also a good electrical conductor. The polymer padis placed over the electrode on the defibrillator paddle. Then thepaddle with the polymer pad thereon is placed over the patient's chest.The tackiness of the polymer pad causes the defibrillator paddle toadhere to the pad and also causes the polymer pad to adhere to thepatient's chest, thereby providing a good electrical contact between thepaddle and the chest.

Therefore, a primary object of the present invention is the provision ofan improved defibrillator pad assembly and method for using same.

A further object of the present invention is the provision of adefibrillator pad assembly which utilizes conductive pads having a tackyundersurface, but having an upper surface which is substantially lesstacky so that the defibrillator paddles can be easily removed from thepad.

A further object of the present invention is the provision of animproved defibrillator pad assembly which utilizes pads which can bequickly adhered to the patient's chest and left there for a period oftime during transporting of the patient.

A further object of the present invention is the provision of animproved defibrillator pad having an adhesive electrically conductivepolymer on its lower surface and having a layer of filamentous carbonfabric on its upper surface.

A further object of the present invention is the provision of animproved defibrillator pad assembly and method for using same which iseconomical, efficient in operation, and inexpensive.

SUMMARY OF THE INVENTION

The present invention utilizes a laminated pad comprising a conductivepolymer layer and a conductive filamentous carbon layer. The polymerlayer is on the bottom of the pad, and is preferably a conductivepolymer which can be purchased from Promeon Division of Medtronic, Inc.,6951 Central Avenue, N.E., Minneapolis, Minn. 55440, under the productdesignation RG 63 A, RG 36 B, or RG 36 T, the latter being the preferredpolymer. The conductive polymer includes thin fibers of polyethylenescrim which run through the polymer and which give the polymer sheetsstrength. The scrim may also be made of other materials such as carbon,nickel, coated-carbon, or other materials.

The conductive pad is shaped to fit the metal electrodes of the paddle,or it can be slightly larger than the electrodes of the paddles. Theconductive pad has a strong tacky characteristic which causes it toadhere to the patient's skin, but the filamentous carbon upper layer isless tacky, thereby permitting the defibrillator paddles to be placed onthe defibrillator pad and removed from the defibrillator pad a pluralityof times.

The filamentous carbon layer is preferably a nonwoven fabric comprising100 percent carbon fibers, and having a density of approximately 0.35ounces per square yard to 0.5 ounces per square yard. The filamentousfiber fabric provides good electrical conductivity, and it also permitssmall protrusions of the polymer there below to protrude upwardlythrough voids which are in the filamentous carbon fabric. This providesa mild tackiness to the upper surface, so as to minimize the tendancy ofthe defibrillator paddle to slip.

If the filamentous carbon layer is uncoated, there is a possibility thatminor sparking may occur between the various carbon fibers duringdefibrillation. While this minor sparking does not affect thedefibrillation process, it is a concern to physicians and paramedicsbecause the sparking could create safety hazards in an environment whereoxygen or other volatile materials might be used. In order to minimizethe risk of sparking, the filamentous carbon mesh is soaked in a liquidsolution of conductive polymer so as to thoroughly wet the filamentouscarbon fiber. The fiber is then removed from the solution and permittedto dry. After drying, the various fibers within the filamentous carbonfiber fabric are coated with the conductive polymer. It has been foundthat treating the filamentous carbon fiber fabric in this manner reducesand in nearly all cases eliminates the sparking between the carbonfibers during defibrillation.

Any conductive polymer will work in the above method so long as it doesnot react to the carbon during the soaking operation. The preferredconductive polymer is a custom made product purchased from Promeondivision of Medtronic, Inc., 6951 Central Avenue, N.E., Minneapolis,Minn. 55440, under the trade designation "5% Poly NaAMPS". This productis diluted with water in a ratio of nine parts water to one part polymerby volume. It is then put into a container to which the carbon fibersare added and soaked. After the soaking of the fibers, the fibers arerolled out on a table and allowed to dry.

A modified form of the invention utilizes an upper layer ofnickel-coated filamentous fibers. The nickel coating of the carbonfibers slightly enhances the electrical conductivity of the fabric.

Normally the defibrillator pad of the present invention is storedbetween a bottom release liner and a top release liner to maintain theadhesiveness of the pad and to prevent dirt or other materials fromadhering to the pad. The release liners are each treated with a siliconefilm which permits them to be separated easily from the tacky polymer ofthe defibrillator pad. When it is desired to use the pad, the toprelease liners are removed from the pad, and the pad itself is removedfrom the bottom release liner. The pad is then placed on the patient'schest with the polymer facing down so as to cause the pad to adhere tothe patient's chest. Tackiness of the polymer will cause the pad toremain on the patient's chest without further aid from the operator. Theoperator then takes the defibrillator paddle and places the electrode ofthe paddle downwardly on the upwardly presented carbon surface of thedefibrillator pad. Electrical continuity is provided between thedefibrillator electrode and the patient's chest by virtue of thelaminated structure of the upper layer of carbon fabric and the lowerlayer of polymer which comprise the defibrillator pad.

After the defibrillator paddle has been used to provide an electricalshock to the patient, the paddle can be removed easily due to theminimal tackiness which is presented on the upper surface of thelaminated pad. A certain minimal amount of tackiness is, however,provided due to the fact that there are certain voids in the carbonfabric which permit the polymer to exude upwardly and be partiallyexposed through the filamentous carbon. This minimal tackiness preventsthe paddles from sliding laterally during their operation, but thetackiness is slight enough to permit easy removal of the paddles afterthe paddles have been used.

The defibrillator pads can be left on the patient's skin duringtransporting to the hospital so that they will be in place in the eventa second defibrillation operation is required.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the defibrillator pad of the presentinvention.

FIG. 2 is a partial sectional view showing the defibrillator pad on apatient's chest with a defibrillator paddle positioned upwardly abovethe patient.

FIG. 3 is an enlarged partial perspective view showing the voids in theupper filamentous carbon layer of fabric.

FIG. 4 is a sectional view taken along line 4--4 of FIG. 3.

FIG. 5 is a sectional view showing a modified form of carbon fiberutilizing a nickel coating on the outer surface thereof.

FIG. 6 is a sectional view of a carbon fiber which has been coated witha conductive polymer.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, the numeral 10 generally designates thedefibrillator pad of the present invention. Pad 10 comprises an uppercarbon fabric layer 12 and a lower polymer layer 14. Pad 10 is shownpackaged between a bottom release liner 15 and a transparent top releaseliner 17. Release liners 15, 17 are treated with a silicone film so thatthey can be easily removed from pad 10.

The lower polymer layer 14 is a conductive polymer purchased fromPromeon Division of Medtronic, Inc., 8299 Central Avenue, N.E.,Minneapolis, Minn. 55432, under the product designation RG 63 A, or RG63 B. The conductive polymer includes thin fibers of polyethylene scrimwhich run through the polymer and which give the polymer sheet strength.The scrim may also be made of other materials such as carbon,nickel-coated carbon, or other materials.

The upper carbon layer is comprised of a fabric made from a plurality ofindividual carbon fibers 13. The fibers 13 are preferably not woven, butare matted together in an irregular configuration. Preferably the fabricis very thin, having a density of 0.35 ounces to 0.5 ounces per squareyard. Due to the thinness of the carbon layer 12, the polymer of thelower polymer layer 14 exudes upwardly through small openings or voids20 so as to create a plurality of protrusions 22 of polymer which areexposed upwardly through the fabric. The existence of the carbon fabricover the top of the polymer inhibits the tacky characteristics of thepolymer on its upper surface so that it will not stick or adherestrongly to another object. However, the fact that some protrusions 22of the polymer protrude through the carbon fabric gives the carbonfabric a slightly tacky or nonslip surface.

If the filamentous carbon layer is uncoated, there is a possibility thatminor sparking may occur between the various carbon fibers duringdefibrillation. While this minor sparking does not affect thedefibrillation process, it is a concern to physicians and paramedicsbecause the sparking could create safety hazards in an environment whereoxygen or other volatile materials might be used. In order to minimizethe risk of sparking, the filamentous carbon mesh is soaked in a liquidsolution of conductive polymer so as to thoroughly wet the filamentouscarbon fiber. The fiber is then removed from the solution and permittedto dry. After drying, the various fibers within the filamentous carbonfiber fabric are coated with the conductive polymer. It has been foundthat treating the filamentous carbon fiber fabric in this manner reducesand in nearly all cases eliminates the sparking between the carbonfibers during defibrillation.

Any conductive polymer will work in the above method so long as it doesnot react to the carbon during the soaking operation. The preferredconductive polymer is a custom made product purchased from Promeondivision of Medtronic, Inc., 6951 Central Avenue, N.E., Minneapolis,Minn. 55440, under the trade designation "5% Poly NaAMPS". This productis diluted with water in a ratio of nine parts water to one part polymerby volume. It is then put into a container to which the carbon fibersare added and soaked. After the soaking of the fibers, the fibers arerolled out on a table and allowed to dry. Referring to FIG. 6, a typicalcarbon fiber 13 is shown having the conductive polymer 28 coatedthereon.

FIG. 2 illustrates the manner in which the device is used. When it isdesired to defibrillate a patient, the transparent layer 17 is peeledback and removed as shown in FIG. 1. Then the pad 10 is peeled off ofthe backing layer 15, and is placed on the exposed skin surface 21 of apatient's chest as shown in FIG. 2. A thin strip 30 of non-tackymaterial is superimposed over the polymer layer 14 along one edgethereof so as to permit the operator to grasp pad 10 withoutencountering the tackiness of polymer layer 14. The polymer layer isplaced downwardly in contact with the skin surface 21 of the patient'schest, and its tackiness causes it to adhere to the skin surface tightlyso as to provide a positive electrical connection therewith.

Then a defibrillator paddle 16 having an electrode surface 18 is placedon top of the carbon layer 12 as shown in FIG. 2. Placing the electrode18 in electrical contact with the carbon layer 12 provides electriccontinuity through the carbon layer 12 and the polymer layer 14 to thepatient's chest. While the electrode 18 does not stick strongly to thepad, the fact that small mounds or protrusions 22 of the polymer exudethrough the voids 20 in the carbon layer provides a substantiallynonslip surface for the electrode 18.

The electrode is then used to defibrillate the patient, and then it canbe removed from the patient after the defibrillation is complete. Thepads 10 stay in place on the patient, and can be kept in place until thedanger of further fibrillation has passed. If defibrillation is needed asecond time, all that is necessary is to replace the paddles on thecarbon layers 12 and repeat the defibrillation process.

The present invention provides the important features of repeatabilityand dependability. The defibrillation process can be repeated numeroustimes with equally good results due to the good electrical contact whichis obtained through the carbon layer 12 and the polymer 14. Furthermore,the device is dependable in that because of good electrical contactbeing made the defibrillation process occurs without burning or damagingthe patient.

Referring to FIG. 5, modified form 24 of the carbon filaments is shown,wherein each carbon filament 13 includes a nickel coating 26 on theouter surface thereof. The nickel coating enhances the electricalconductivity of the pad. While 100 percent carbon fabric will worksatisfactorily, the nickel coating improves the conductivity byapproximately two to five percent.

If nickel coating is used for the fibers, it is possible to use amaterial other than carbon for the fibers themselves since the nickelwill provide the electrical conductivity necessary to provide arepeatable and dependable defibrillation. Thus, it can be seen thedevice accomplishes at least all of its stated objectives.

I claim:
 1. A method for preparing a patient's chest having an exposedskin surface for accepting a defibrillator paddle, said methodcomprising:taking a laminated defibrillator pad having a bottom layer ofelectrically conductive polymer which is tacky so as to adhere to mostsurfaces it contacts, said pad having an upper layer comprising fabricmaterial formed from filamentous carbon fibers which are coated with afilm of electrically conductive polymer, said upper layer being adheredto and in electrical contact with said bottom layer; placing said pad onsaid patient's chest with said bottom layer in contact with said exposedskin surface of said patient's chest whereby said tackiness of saidbottom layer will cause said pad to be detachably adhered to and inelectrical contact with said exposed skin surface of said patient'schest; and placing said defibrillator paddle in facing engagement withand in electrical contact with said upper layer of said pad whereby saidpad will provide electrical continuity from said defibrillator paddle tosaid exposed skin surface of said patient.
 2. A method according toclaim 1 and further comprising removing said defibrillator paddle fromelectrical contact with said upper layer of said pad, said upper layerat least partially shielding said defibrillator paddle from saidtackiness of said bottom layer whereby said pad will remain adhered tosaid exposed skin surface after removal of said defibrillator paddlefrom said upper surface.
 3. A method according to claim 2 and furthercomprising using pure carbon for said filamentous carbon fibers of saidupper layer.
 4. A method according to claim 2 and further comprisingusing nickel plated carbon for said filamentous carbon fibers of saidupper layer.
 5. A defibrillator pad for use between an exposed skinsurface of a patient's chest and a planar electrode surface of adefibrillator paddle, said defibrillator pad comprising:a laminateddefibrillator pad having a bottom layer and an upper layer; said bottomlayer being comprised of an electrically conductive polymer which istacky so as to adhere to most surfaces it contacts; said upper layercomprising fabric material formed from filamentous carbon fibers, saidfabric material having a plurality of openings therein; said bottomlayer having a flat downwardly presented surface for engaging andadhering to said patient's chest with a first predetermined force, andhaving an upwardly presented upper surface in contact with said upperlayer; said conductive polymer of said upper surface of said bottomlayer exuding through said openings of said upper layer so as to form aplurality of polymer protrusions which are exposed upwardly through saidopenings of said upper layer; said polymer protrusions and said fabricof said upper layer combining to form an upwardly presented planarelectrode engaging surface capable of engaging and covering saidelectrode surface of said defibrillator paddle and capable of adheringto said electrode surface with a force less than said firstpredetermined force at which said downwardly presented surface of saiddefibrillator pad will adhere to said exposed skin surface of saidpatient's chest.
 6. A defibrillator pad according to claim 5 whereinsaid upper layer comprises 100 percent carbon.
 7. A defibrillator padaccording to claim 5 wherein said upper layer comprises nickel-platedcarbon.
 8. A defibrillator pad according to claim 5 wherein said fabricmaterial comprises carbon fibers having a density of from 0.35 ouncesper square yard to 0.5 ounces per square yard.
 9. A defibrillator padaccording to claim 5 wherein said filamentous carbon fibers of saidupper layer are coated with a film of electrically conductive polymer.10. A defibrillator pad according to claim 5 wherein said fabricmaterial of said upper layer comprises a plurality of said filamentouscarbon fibers matted together in an irregular configuration.
 11. Adefibrillator pad according to claim 5 wherein said fabric material hasa density of from 0.35 ounces to 0.5 ounces per yard.
 12. A combinationadapted to be applied to an exposed skin surface of a patient's chestcomprising:a laminated defibrillator pad having a bottom layer ofelectrically conductive polymer which is tacky so as to adhere to mostsurfaces it contacts, said pad having an upper layer comprising fabricmaterial formed from filamentous carbon fibers which are coated with afilm of electrically conductive polymer; said bottom layer being adaptedto be in contact with said exposed skin surface of said patient's chestwhereby said tackiness of said bottom layer causes said bottom layer tobe detachably adhered to and in electrical contact with said exposedskin surface; said upper layer having openings therein; said bottomlayer exuding upwardly through said openings so as to create a pluralityof protrusions which are exposed upwardly through said openings of saidupper layer; a defibrillator paddle having an electrode surface infacing engagement with and in electrical contact with said upper layerof said pad and said protrusions of said bottom layer which are exposedupwardly through said openings of said upper layer; said upper layer atleast partially shielding said defibrillator electrode surface from saidtackiness of said bottom layer whereby said electrode surface adheres tosaid defibrillator pad with an adhering force which is less than theadhering force between said bottom layer and said exposed surface ofsaid patient's skin.